Tarnopolsky Mark A, Safdar Adeel
Department of Pediatrics and Medicine, McMaster University, HSC-2H26, 1200 Main St. W., Hamilton, ON L8N 3Z5, Canada.
Appl Physiol Nutr Metab. 2008 Feb;33(1):213-27. doi: 10.1139/H07-142.
Human aging is associated with a significant reduction in muscle mass (sarcopenia) resulting in muscle weakness and functional limitations in the elderly. Sarcopenia has been associated with mitochondrial dysfunction and the accumulation of mtDNA deletions. Resistance training increases muscle strength and size and can increase mitochondrial capacity and decrease oxidative stress in older adults. Creatine monohydrate (CrM) and conjugated linoleic acid (CLA) have biological effects that could enhance some of the beneficial effects of resistance training in older adults (i.e., up arrow fat-free mass, down arrow total body fat). We have completed two resistance-training studies with CrM alone and CrM+CLA supplementation in older adults to evaluate the independent effects of exercise and dietary supplements, as well as their interactive effects. Our studies, and several others, have found that CrM enhanced the resistance exercise mediated gains in fat-free mass and strength. More recently, we found that the addition of CLA also lead to a significant reduction of body fat after six months of resistance training in older adults. Older adults have fewer wild-type mtDNA copies and higher amounts of mtDNA deletions as compared with younger adults in mature skeletal muscle; however, these deletions are not seen in the satellite cell-derived myoblast cultures. These findings, and the fact that mtDNA deletions are lower and wild-type mtDNA copy number is higher after resistance training in older adults, suggests that activation of satellite cells secondary to resistance exercise-induced muscle damage can dilute or "shift" the proportion of mtDNA genotype towards that of a younger adult. Recent evidence suggests that CrM supplementation in combination with strength training can enhance satellite cell activation and total myonuclei number per muscle fiber in young men. Future studies are required to determine whether the mitochondrial adaptations to resistance exercise in older adults are further enhanced with CrM supplementation and whether this is due to increased recruitment of satellite cells. It will also be important to determine whether these changes are maintained over a longer time period.
人类衰老与肌肉量显著减少（肌肉减少症）相关，这会导致老年人肌肉无力和功能受限。肌肉减少症与线粒体功能障碍以及线粒体DNA缺失的积累有关。抗阻训练可增加老年人的肌肉力量和围度，并能提高线粒体功能以及降低氧化应激。一水肌酸（CrM）和共轭亚油酸（CLA）具有生物学效应，可能会增强抗阻训练对老年人的一些有益作用（即增加去脂体重，减少全身脂肪）。我们已完成两项针对老年人单独使用CrM以及补充CrM+CLA的抗阻训练研究，以评估运动和膳食补充剂的独立作用及其交互作用。我们的研究以及其他一些研究发现，CrM可增强抗阻运动介导的去脂体重和力量增加。最近，我们发现，在老年人进行六个月的抗阻训练后，添加CLA也能显著减少体脂。与年轻成年人相比，老年人成熟骨骼肌中的野生型线粒体DNA拷贝数较少，线粒体DNA缺失量较多；然而，在卫星细胞衍生的成肌细胞培养物中未观察到这些缺失。这些发现，以及老年人抗阻训练后线粒体DNA缺失减少且野生型线粒体DNA拷贝数增加这一事实，表明抗阻运动诱导的肌肉损伤继发的卫星细胞激活可稀释或“改变”线粒体DNA基因型的比例，使其向年轻成年人的比例转变。最近的证据表明，在年轻男性中，补充CrM与力量训练相结合可增强卫星细胞激活以及每条肌纤维的总肌核数。未来的研究需要确定，补充CrM是否能进一步增强老年人抗阻运动后的线粒体适应性，以及这是否归因于卫星细胞募集增加。确定这些变化是否能在更长时间内维持也很重要。
